It is therefore of interest to identify any particular characteristics of DBA patients which might delay or hinder the application of gene therapy to their disease. This pilot study of 15 patients is designed to evaluate: 1) the CD34+ cell mobilization response to administration of standard doses of granulocyte-colony stimulating factor (G-CSF), 2) the potential for stem cells from DBA patients to be collected by large volume leukapheresis of subjects who have been given G-CSF, and 3) the ability of these G-CSF mobilized cells to be transduced with vectors being developed for gene therapy applications. Outcome parameters to be monitored are the mobilization response to G-CSF, the safety profile and tolerance of G-CSF and leukapheresis, and the efficiency of transduction of DBA stem cells with standard gene therapy vectors. Effectiveness will be gauged by historical comparison of these parameters to normal healthy age-matched volunteer.